The ability of selected silicone-based polymers to dissolve human cholesterol and bilirubinate gallstones in vivo will be assessed. Gallstones will be categorized as predominately cholesterol type or bilirubin type based on color. Weight-matched sets of four stones will be incubated in buffer, sodium cholate, monooctanoin and in a series of silicone-based polymers. Weight loss will be followed for a period of up to three weeks. Any polymer which compares favorably to monooctanoin with regard to the dissolution rate for cholesterol stones will be suggested as a candidate for Phase II study. Polymers that dissolve bilirubinate stones at any rate will be considered candidates for Phase II study. One polymer has been shown to promote the dissolution of bovine bilirubinate stones in a brief in vitro experiment. Phase II research will be directed toward preclinical qualification sufficient to warrent IND investigation of a safe polymeric solvent for bilirubinate stones that is compatible with monooctanoin. Such a mixed solvent has potential to dissolve all retained gallstones. Follow-on funding will be evaluated as soon as a polymer is identified that meets the development selection criteria.